One known type of engine control system for an automotive engine with an engine driven complementary device or system, such as an automotive air conditioning system including an air compressor releasably connected to the automotive engine by an electromagnetic clutch, forcibly actuates the electromagnetic clutch to disconnect the compressor from the automotive engine when an accelerator is overly depressed during acceleration to thereby decrease engine load so as to ensure the accelerative ability of the automotive engine. Such an engine control system is described in Japanese Patent Publication No. 59(1984) - 5445.
Meanwhile, when operating at high elevations, a fuel mixture delivered into the automotive engine tends to become overly rich in that the air becomes thinner and contains less oxygen to sustain burning. This results in a deterioration of the automotive engine acceleration ability. For this reason, when the automotive engine operating at high elevations is required to accelerate or rapid increase in speed, the accelerator is depressed frequently. In the automotive engine having the same type of engine control system as described above, the electromagnetic clutch is also actuated to frequently disconnect the compressor of the automotive air conditioning system from the automotive engine. Such a frequent operation of the accelerator causes hunting of the automotive engine due to changes in engine load.
Because the amount of air in the fuel mixture becomes thinner when the automotive vehicle operates at high elevations when compared to operating at low elevations, the automotive engine, for example in idling, loses speed and possibly stops due to an increase in engine load when the automotive air conditioning system operates while an oil pump is simultaneously actuated, for example, in driving a power steering unit.